Lecture 16 Flashcards
What is the difference between mycobacterium tuberculosis and Mycobacterium Bovis?
Mycobacterium Bovis is derived from animals while Mycobacterium tuberculosis can spread from human to human
What type of disease is caused my Mtb?
Slow, Progressive disease
Does Mtb stain gram positive or negative?
Mycobacterium does not take up the gram stain
How many organs does Mtb typically infect within one person?
One, although it is usually spread throughout the body
What is the key feature seen in Cavitating Pulmonary Tb?
Many large abscesses are seen in the lung
What is seen in Miliary pulmonary tb?
Nodules of disease scattered throughout the lung
What has caused the decline in the incidence of tb?
Better style of living, NOT due to improved treatments
Is Tb still decreasing and why?
No there has been a resurgence, mainly due to immigration of people from countries with lower quality of living introducing the disease to those who have not previously been susceptible
What percentage of the worlds population is infected with Tb and how many of these people are likely to develop the disease?
1/3 of the worlds population is infected and roughly 1/10 people go on to develop the disease
What fraction of adult deaths was tb responsible for in the 1800s?
1/3
What are the steps of pathogenesis in Tb?
The tb is inhaled and settles in the alveoli where it is ingested by and alveolar macrophage,
A virulence of the Tb prevents the phagosome from fusing with the lysosome allowing the Tb to replicate until the macrophage dies, this releases the bacilli allowing them to repeat the process with other macrophages
T helper cells are recruited resulting in the initiation of the inflammation process
Granuloma formed
Stable granuloma formed if multiplication of the Tb is equal to the killing and destruction of Tb
Occasionally a granuloma will grow causing tissue destruction and wasting
What are the two methods that results in the enlargement of the granuloma?
T cells are compromised therefore the ability of macrophages to kill the Tb is also compromised
The granuloma pierces a bronchiole resulting in an increased oxygen supply improving their ability to replicate and overcome the immune system
What methods can be used to identify Tb?
The Ziehl-Neelsen stain will result in red staining of Tb
The Tb can cultured though this is limited due to the slow (24 hour) replication rate of the bacterium
PCR can amplify DNA to detect the Tb bacterial DNA
What tests can be used to diagnose if there has been a Tb infection?
Mantoux and Quantiferon tests
What is the mantoux test (tuberculin skin test)?
Some of the membrane of the Tb bacillus is injected into the person and swelling will occur if there had been a Tb infection
